In general, whether the locomotive is an electric locomotive or a diesel locomotive, the method of car body construction of a locomotive can be roughly divided into two types. One of these is the method called the “box type car body system” and the other is the method called the “bonnet (or hood) type car body system”.
The box type car body system is a monocoque car body system in which a single car body is constituted by a car body under-frame and a steel car body that is welded with the car body under-frame on top of the car body under-frame.
Also, the bonnet type car body system is a system in which a unitary bonnet 20 (for example as shown in Laid-open Japanese Patent Application Tokkai 2008-95515 (hereinafter referred to as Patent Reference 1)) having a door 21, in the form of a unitary cover as shown in FIG. 10, or a divided type bonnet (not shown) obtained by dividing the bonnet 20 into a plurality of divided bonnets is used for the locomotive. The unitary or divided bonnet type car body system is a car body system in which the bonnet 20 is screwed on so as to cover from above the equipment that is arranged in the car body under-frame 3, and in which passages are provided at the outer peripheral side of the bonnet 20 for purposes of for example inspection. As this bonnet type car body system, a “center cab system” or “semi-center cab system” may be adopted, depending on the position of the driver's cab.
Typically, in the case of mainline locomotives, driver's cabs are provided at both the front and rear ends of a vehicle in which a box type car body system is adopted, in order to provide a forward field of view from the driver's cab. On the other hand, in the case of shunting locomotives that are mainly used for shunting, in which the direction of drive is frequently changed during for example a shunting task, the driver's cab is arranged substantially in the middle in the direction of travel of a vehicle in which a bonnet type car body system is adopted.